This work compares the effects of two forms of ultraviolet lasers (KrF and XeCl) on fresh human cadaver coronary arteries in an attempt to see if differences due to stronger protein and nucleic acid absorption in the mid UV range would favor the 248nm KrF laser for subsequent in vivo investigation. We found that both excimer lasers produced selective abaltive tissue effects with minimal thermal difusion. However, the initial ablative threshold and near maximal ablative efficiency required more than twice the energy density with XeCl compared to KrF lasers. This may have important implications in the ultimate choice of a laser source. Improved ablative effects with KrF probably results from enhanced linear absorption but need to be viewed in the context of great mutagencity and lower fiber damage threshold at 248nm which may offset such advantages.